1. Field of the Invention
This invention relates to a communication system (“network”) that accommodates wrapped packets, each of which includes error control bits that, in conjunction with unique identifiers assigned to each module or switch connected to the network, detect the location at which the network is severed and yet maintains efficient transfers across the network.
2. Description of the Related Art
A communication network is generally regarded as an interconnected set of subnetworks or subnets. The network can extend over localized subnets as an intranet or can extend globally as an internet between one or more intranets. A communication network can therefore forward data within a localized network between termination devices extending to almost anywhere around the world. The termination devices include any data entry/retrieval system (e.g., telephone or computer), and a network includes a local and/or global interconnection of termination devices configured on one or more subnets.
Each subnet or interconnected set of subnets can be configured in various ways. For example, the subnets can be arranged in a ring, star, mesh and/or linear topology. Furthermore, the topography can accommodate various transmission protocols. A popular communication protocol includes the Transmission Control Protocol (“TCP”) and the Internet Protocol (“IP”). Protocols such as TCP/IP determine how the termination devices will communicate with each other over the network that may be configured with or without internet connection.
Popular protocols such as TCP/IP deliver data across the network in the form of a packet. Each packet of a particular message may be sent across different routes of the network at the same time, and then reassembled at the proper termination device. In order to ensure the packets are properly received, certain layers of the popular Open System Interconnect (“OSI”) protocol stack will wrap the data before the packet is sent across the network. For example, TCP can divide data into segments that are then placed into, for example, IP datagrams having a segment of data interposed between a header and a trailer. The combination of header, data segment, and trailer is interchangeably called the IP datagram or “packet.” The IP datagram can be further wrapped using a Point-to-Point Protocol (“PPP”), a popular such protocol being that which follows the Ethernet specification at the physical layer. Thus, it is not until the data segment has been wrapped possibly numerous times will the packet be forwarded across the network.
Once the packet has been properly wrapped, it will in most instances be forwarded unhindered across the network. Unfortunately, however, transmission disruptions can often occur. Such might be the case where a transmission path of the network is severed, or otherwise temporarily or permanently disabled. If the disrupted path is in a critical segment of the network, it may be impossible to reroute a packet between termination devices while avoiding that path. Thus, even with networks having more than several alternative routes between a pair of termination devices, a disrupted critical route would disable the entire network transmission.
In an effort to obviate temporary or permanent network downtime resulting from a disturbed (i.e., corrupted, disabled, or severed) transmission path, many architectures use redundancy. For example, in a ring topology, transmission from one station to another station connected to the ring proceeds in a single direction around the ring. If the transmission channel is disturbed, transmissions between those stations can no longer take place if, indeed, those stations are separated by the disruption. Using a second, or “redundant,” channel, redundant packets can be sent in both directions on both channels around the ring. Thus, if the left transmission channel is cut, the right transmission channel is able to maintain transmission in the right direction around the ring. In an implementation of dual ring topology, data packets can be sent in both directions simultaneously. One direction can be designated as the primary transmission direction. Normally, packets will be received from this path. Packets received from the other path will be dropped at the receiver end. However, if there is a disruption in the primary direction, the receiver will receive the packet via the alternate direction. An alternative example may be a star or mesh topology, whereby transmission can proceed from station A to station B either directly or, if the channel separating stations A and B is disturbed, then transmission can proceed through a redundant channel such as from station A to station C and station C to station B.
As used hereinbelow, a transmission path includes two or more alternative transmission channels, where one channel is the primary channel and the other channels can be considered redundant channels. Each channel is deemed either a copper conductor, fiber or wireless transmission medium. In a ring topology, the primary and redundant channels can be formed in a single transmission path around the loop. In a mesh topology, transmission channels can exists between each of n−1 number of stations, where n equals the number of stations within the star. In a mesh topology, transmission channels exist between each pair of n stations. In the star or mesh topology, the redundant transmission channel can be the alternative pathway between two stations via other stations.
In physical fiber optic implementation, a single fiber will consist of multiple strands and each strand consists of multiple Wave Division Multiplex (WDM) channels. A physical cut (or severance) of the fiber will generally result in disruption of services for all channels associated with that fiber. Frequently, this will result in disruption of service in both primary and redundant channels at that point. In a ring topology, there is a significant likelihood that both the primary and redundant channels will be disrupted, rather than a single channel since both channels are typically located next to one another around the ring. For example, both the primary and redundant channels can be clad in a unitary structure, and whenever one is cut it is most likely that the other channel will also be cut thereby rendering useless the entire redundancy feature. Therefore, even though Synchronous Optical Networks (“SONET”) employ redundant optical fibers, a disruption of both the primary and redundant fiber can, at the very least, reduce the overall transmission bandwidth or, in the extreme, prevent transmission altogether. Using the former instance and the aforesaid example, if both the left and right fibers are cut between stations A and B, station A can still send information across, for example, the right fiber to station B, and can send packets across the left fiber to an intermediate station upstream of the cut. Unfortunately, packets sent in the left and right fibers are redundant of each other. So, even though the overall bandwidth capacity is 5 Gbits, the maximum bandwidth achievable using the SONET redundant system is 2.5 Gbits. This is due to one set of packets being sent on the left channel and the very same (redundant) set of packets being sent on the right channel.
It would be desirable to introduce a redundant system that does not send the same (i.e., redundant) packets across both left and right channels in a ring topology. Instead, the desired system would use two channels to be routed around the ring or between each mesh- or between most star-configured stations, but allow each channel to be utilized for data transmission. This would maximize the bandwidth capacity of the network or communication system. If each channel is to be utilized, then the desired system should be one which still permits non-redundant transmission to all stations, regardless of where within the network one or both channels are disturbed (i.e., severed, disrupted or otherwise disabled). The improved system, method, architecture, and packet protocol must desirably not only maintain packet transmission speed, but must also note where within the network the severed transmission path exists so as to re-route future packets to avoid the disturbed channel.